SEVERE THUNDERSTORMS

Hot, humid, unsettled weather conditions. An approaching cold front or trough. The ideal conditions for severe thunderstorms, and their progeny of flash flooding, large hail, destructive wind gusts, and even tornadoes. Most Australians can vividly recall at least one major thunder-, wind- or hailstorm in their area, and occasionally these storms are of such note to be talked about for many years afterwards. In Melbourne, the February 1972 flash flood was such a storm; in Brisbane, the tornado of November 1973, in Sydney, the 1990 and 1999 hailstorms.

Dust-storms, too, are a memorable event on the relatively rare occasions they affect coastal districts, as can occur during severe drought periods. Dust-storms were frequent during the extended dry period of the 1930s and 1940s: in the summer of 1944/45, dust was on several occasions so thick in Adelaide that street lighting had to be turned on!

Hail packs the streets like snow - Day St, Sydney, morning of 21 August 1971
(photo courtesy of "Emergency Management Australia")

Storm damage
According to Emergency Management Australia, severe thunderstorms cause more damage in Australia each year than any other natural hazard, and the damage bill in individual cases has gone into the hundreds of millions of dollars. Hail causes the greatest proportion of the damage, accounting for nearly half the total losses from severe storms. Insurance losses in the storm of 14 April 1999 exceeded $1.5 billion.

When are severe storms most likely?
Although all parts of Australia experience severe thunderstorms, their preferred time of occurrence varies. In most of northern Australia, autumn and spring are the most likely time, in eastern Australia it is the late spring/summer period. In southwestern Australia, they are most common in winter in areas nearer the coast, but in spring-early summer further inland. As a rule, severe storms are most common in New South Wales, Queensland and parts of Western Australia, and least common in Tasmania.

The Fujita scale of tornado intensity.

Title image - A dust-storm rolls across Mildura (Victoria) at the height of the severe 1967/68 drought in southeastern Australia. (Photo courtesy of the Sunraysia Daily.

cyclone | storm | drought | flip side | flood | temperature | fire